This project directly addresses the call by NIH for the development and characterization of models specifically suited to study the impact of FMR1 premutation on ovarian insufficiency. The Fragile X Mental Retardation 1 gene (FMR1) contains a series of approximately 30 CGG triplet repeats located in the 5' UTR. Mutational expansion of the number of CGG repeats to greater than 200 triplets leads to Fragile X Syndrome. The focus of the present studies is the premutation expansion of the CGG repeats to between ~40 and 200, and its association with ovarian insufficiency. Significant data describe reproductive insufficiencies including premature ovarian failure in women carrying the FMR1 premutation expansion. The association between pre- mutation expansion and reproductive insufficiencies was made recently and thus there is currently no understanding of the mechanisms whereby this premutation result in altered reproductive capacity in women. Our objective is to identify models that will be useful in defining the role of FMR1 premutation in female reproduction. The proposed project has two specific objectives. Aim 1 will take advantage of an existing mouse model of fragile X premutation and fully characterize female fertility. The objective is to assess reproductive parameters analogous to those documented in women in order to establish the significance of the mouse model and its relationship to reproduction. The studies carried out in Aim 2 will create conditional knock-ins carrying premutation expanded CGG repeats targeted to the granulosa, anterior pituitary, and oocyte. Studies in women indicate each of these cell types may be impacted by the premutation and thus play a role in the resulting ovarian insufficiency. The granulosa, oocyte, and anterior pituitary form key components of the hypothalamic-pituitary-ovarian endocrine system important for normal fertility. Targeting to each cell type individually will allow us to carefully assess the contribution of the premutation in each cell type as it relats to the reproductive process. A novel transgenesis method relying on the use of the Streptomyces phage C31 (?C31) site specific integrase to direct transgene integration will be used to generate the conditional transgene. In production of the targeted premutation mice we will generate a conditional transgenic mouse that will be a tool for the greater research community allowing for targeting of the premutation expansion to any tissue or cell type. We have an assembled research team with expertise in female reproductive biology, mouse genetics, and the fragile X patient population and together we are poised to address this directed call by NIH. With the completion of these studies we will have both global and targeted premutation expansion mouse models specifically suited to explore the mechanisms whereby FMR1 premutation impacts the reproductive system in women.